Soft silicone hydrogel contact lenses are increasingly becoming popular because of their high oxygen permeability and comfort. But, a silicone hydrogel material typically has a surface, or at least some areas of its surface, which is hydrophobic (non-wettable) and susceptible to adsorbing lipids or proteins from the ocular environment and may adhere to the eye. Thus, a silicone hydrogel contact lens will generally require a surface modification.
A known approach for modifying the hydrophilicity of a relatively hydrophobic contact lens material is through the use of a plasma treatment, for example, commercial lenses such as Focus NIGHT & DAY™ and O2OPTIX™ (CIBA VISION), and PUREVISION™ (Bausch & Lomb) utilize this approach in their production processes. Advantages of a plasma coating, such as, e.g., those may be found with Focus NIGHT & DAY™, are its durability, relatively high hydrophilicity/wettability, and low susceptibility to lipid and protein deposition and adsorption. But, plasma treatment of silicone hydrogel contact lenses may not be cost effective, because the preformed contact lenses must typically be dried before plasma treatment and because of relative high capital investment associated with plasma treatment equipment. Further, plasma treatment may not provide a silicone hydrogel contact lens with a desirable surface lubricity.
Another approach for modifying the hydrophilicity of a relatively hydrophobic contact lens material is a layer-by-layer (LbL) polyionic material deposition technique (see for example, U.S. Pat. Nos. 6,451,871, 6,719,929, 6,793,973, 6,884,457, 6,896,926, 6,926,965, 6,940,580, and 7,297,725, and U.S. Patent Application Publication Nos. 2007/0229758A1, US 2008/0174035A1, and US 2008/0152800A1). Although the LbL deposition technique can provide a cost effective process for rendering a silicone hydrogel material wettable, LbL coatings may not be as durable as plasma coatings and may have relatively high densities of surface charges, in particular, negative surface charges; which may interfere with contact lens cleaning and disinfecting solutions due to their high susceptibility to deposition and accumulation of positively charged antimicrobials (e.g., polyhexamethylene biguanide, Polyquaternium-1®, or the like) commonly found in most multipurpose lens care solutions. Those positively charged antimicrobials adsorbed by the silicone hydrogel lenses may be released into the eye and may cause undesirable clinical symptoms in some persons, such as diffuse corneal staining and product intolerance, when the lenses are worn by patients. To improve the durability, crosslinking of LbL coatings on contact lenses has been proposed in commonly-owned copending US patent application publication Nos. 2008/0226922 A1 and 2009/0186229 A1 (incorporated by reference in their entireties). However, crosslinked LbL coatings may have a hydrophilicity and/or wettability inferior than original LbL coatings (prior to crosslinking) and still have relative high densities of negative surface charges.
US Patent Application Publication No. 2008/0142038A1 describes another approach for modifying the hydrophilicity of a relatively hydrophobic contact lens material. According to this approach, a preformed silicone hydrogel contact lens in unhydrated state is subjected to a oxidation plasma treatment in an atmosphere composed of a suitable media, such as, ammonia, an alkylamine, air, water, peroxide, oxygen gas, methanol, acetone, etc., in order to improve or promote adhesion for bonding of the subsequent carboxylic acid-containing polymeric or copolymeric layer; then the plasma-treated lens is extracted in an organic solvent (e.g., isopropanol), rehydrated in water, and packaged in a polypropylene blister pack containing a coating solution of a polyanionic polymer (e.g., polyacrylic acid); and finally the packaged lens is sterilized in steam in an autoclave at a temperature up to and including 100° C. This approach would still have the above-described shortcomings for the LbL-approach, such as, high susceptibility to deposition and accumulation of positively charged antimicrobials in a lens care solution and insufficient durability.
U.S. Pat. No. 6,630,243 disclose another approach for modifying the hydrophilicity of a relatively hydrophobic contact lens material. According to this approach, a preformed silicone hydrogel contact lens in unhydrated state is subjected to plasma polymerization in a hydrocarbon-containing atmosphere to form a polymeric carbonaceous layer on the lens surface; reactive functionalities are then generated on the surface of the carbonaceous layer; and finally a hydrophilic reactive polymer is covalently attached to the surface of the carbonaceous layer through the surface reactive functionalities of the carbonaceous layer. This approach may not provide a silicone hydrogel contact lens with a desirable surface lubricity.
A still further approach for modifying the hydrophilicity of a relatively hydrophobic contact lens material is to attach hydrophilic polymers onto contact lenses according to various mechanisms (see for example, U.S. Pat. Nos. 6,099,122, 6,436,481, 6,440,571, 6,447,920, 6,465,056, 6,521,352, 6,586,038, 6,623,747, 6,730,366, 6,734,321, 6,835,410, 6,878,399, 6,923,978, 6,440,571, and 6,500,481, US Patent Application Publication Nos. 2009/0145086 A1, 2009/0145091A1, 2008/0142038A1, and 2007/0122540A1, all of which are herein incorporated by reference in their entireties). Although those techniques can be used in rendering a silicone hydrogel material wettable, they may not be cost-effective and/or time-efficient for implementation in a mass production environment, because they typically require relatively long time and/or involve laborious, multiple steps to obtain a hydrophilic coating.
Recently, a new cost-effective approach has been described in U.S. pat. Appl. pub. No. 2012/0026457 A1 (herein incorporated by reference in its entirety) for applying a non-silicone hydrogel coating onto a silicone hydrogel contact lens, in which an organic solvent-based coating solution of a polyanionic polymer is involved in forming an interpenetrating base coating (i.e., an anchoring layer) on a silicone hydrogel contact lens and then a partially-crosslinked hydrophilic polymeric material is covalently attached onto the anchoring layer directly in a lens package during autoclave. Although silicone hydrogel contact lenses produced according to such an approach can have a water-gradient structural configuration and a soft and lubricious surface, they may be susceptible to high deposition and accumulation of positively charged antimicrobials commonly found in most multipurpose lens care solutions, due to the presence of the anchoring layer of a polyanionic material.
Therefore, there is still a need for an improved method for producing silicone hydrogel contact lenses with a durable, lubricious non-silicone hydrogel coating which has a minimized susceptibility to high deposition and accumulation of positively charged antimicrobials and which has a low surface friction to result in improved wearing comfort. There is also a need for silicone hydrogel contact lenses with such a durable coating thereon.